All-Atomic Modeling of the Compaction of Montmorillonite Clays: Fabric Evolution and Energy Conversion

Compaction is an essential compression process for sedimentary soils. Compared with in-depth studies on granular soil behaviors, numerical modeling of clay compaction is still in its infancy. This study presents an all-atomic modeling framework to investigate the compaction of anhydrous montmorillonite from initially fully exfoliated platelets. The total number of interparticle contacts increased, and the mesopores were dominant during the formation of card-house structures. As the local fabrics evolved into book-house structures, the contact evolutions became predominant, and partial mesopores transformed into micropores. The coordinated deformations during the formation of compacted aggregates dramatically increased interparticle contacts, and so the micropores became dominant. After rebound, the interparticle contacts decreased and partial micropores were restored. The total potential energy decreased during contact evolutions due to the significant reduction in interaction potential energy between clay particles, while hysteresis was observed during coordinated deformations and rebound due to the changes in internal potential energy within deformed clay particles. The internal potential energy was primarily determined by the electrostatic forces except under significant deformations, where the van der Waals forces became dominant. The interaction potential energy remained unchanged with specific contact types but decreased significantly due to electrostatic interaction when contacts evolved. As computational capacity develops, a greater number of larger hydrated clay particles can be used to improve simulations of compaction and other macroscopic behaviors via all-atomic molecular dynamics simulations.